DEA Coastlines FAQs

Frequently asked questions about Digital Earth Australia (DEA) Coastlines

Last updated:18 June 2024

How accurate is DEA Coastlines?

DEA Coastlines shows changes in the median position of the shoreline at mean sea level tide — the position of the shoreline between low and high tide – each year since 1988. This shoreline is accurate to between 7 to 10 metres in a comparison against 57,000 validation data points across the Australian coastline. Rates of coastal change are accurate to between 0.31 to 0.35 metres per year.

This level of accuracy allows the product to accurately map and monitor long-term changes in coastline positions over time at a scale relevant to local and regional coastal management.

The accuracy of DEA Coastlines is lower in complex and dynamic coastal environments such as intertidal flats, river mouths, rapidly changing sand bars, and where muddy substrates, turbid water and large tidal ranges make it difficult to extract a single, clean coastline.

Cloud cover can also reduce the accuracy of the product by reducing the availability of clear satellite imagery. The data can also be limited over remote islands or reefs due to a lack of historical satellite information.

For detailed information about the accuracy and limitations of DEA Coastlines, refer to the Product Documentation.

DEA Coastlines 2021 dataset incorporates Landsat 9 data and uses a new tidal model. How might this affect my pre-2020 modelling?

The addition of Landsat 9 satellite data to the underlying source data of DEA Coastlines will affect all annual shorelines from 2021 onwards. The additional data is expected to improve the overall quality of the annual shorelines by providing cleaner and more stable annual layers.

The integration of a new global tidal model (FES2014) may result in minor changes to the product’s historical coastlines and derived rates of coastal change. These changes are likely to be greatest in macrotidal regions of Australia such as north-western Western Australia and central Queensland. A comparison of annual shoreline accuracy at the microtidal Narrabeen Beach in Sydney shows consistent results between DEA Coastlines version 1.1.0 and the newer version 2.0.0.

Where specific changes or issues have been identified, they are noted in the Product Documentation.

What causes changing coastlines?

DEA Coastlines presents a historical record of coastal change since 1988 – it does not assign a reason or cause for coastal change or make predictions about future patterns or rates of coastal change.

Coastal change is complex and driven by many interacting factors including local geomorphology (the shape of the local coastline), extreme weather and climatic events such as La Niña, ocean currents, wind patterns, and coastal development.

For example, the construction of new inlets or marinas may be represented in DEA Coastlines as areas of coastline retreat, while the construction of ports or piers may be represented as areas of coastline growth. Rates of change from DEA Coastlines should therefore be evaluated carefully with reference to the underlying annual coastlines, and other more detailed data sources or imagery.

Does DEA Coastlines show the effect of individual storms?

No. DEA Coastlines shows the most representative (median) location of the coastline over an entire year, so does not show the effect of individual major storms. However, DEA Coastlines data can be used to identify coastlines that respond to longer-scale climatic cycles such as El Niño–Southern Oscillation (ENSO). For example, coastlines in eastern Australia may retreat as La Nina conditions increase the likelihood of east coast lows, damaging cyclones and extreme storm surges.

Could DEA Coastlines replace local coastal monitoring surveys?

No. Local on-the-ground and aerial coastal monitoring surveys are still crucial to the management of coastal areas. DEA Coastlines provides an affordable and efficient option for larger-scale planning and for better understanding of long-term coastal trends. Coastal monitoring data provided by local and state government, universities, and citizen science projects has been critical for validating DEA Coastlines.

DEA Coastlines interactive map

Visit DEA Maps to get the full interactive map with DEA Coastlines and other DEA products.